ObjectArx创建自定义实体

一。目的

在ObjectArx中已经有了许多实体，如AcDbLine,AcDbCircle,AcDbArc等，但在用户使用Cad时，会有一些对他们来讲常用的“实体“，如一扇门，如果我们能提供一个“门实体“，让用户能向添加直线一样方便，相信用户是很乐意接受由此功能的软件！这是，我们为这个“门“就相当于一个自定义实体”!(PS:希望没理解错)！

本文将介绍创建一个长方体的自定义实体，支持简单的编辑以及二维，三维显示！

二。相关知识储备

1）既然是自定义实体，那你就必须将其显示出来，来告诉用户你的自定义实体“长”什么样子，如下函数：（与MFC中的OnPaint()有点相似）

virtual Adesk::Boolean subWorldDraw (AcGiWorldDraw *mode) ;扩

可以看出这是一个虚函数，由父类AcDbEntity继承而来，并且绝对需要你重写的函数，与之类似的还有其他几个从父类继承而来的虚函数，理论上都需要重写！

2）由于这里需要绘制长方体，就涉及到面的绘制，可以用到以下二个函数（二者择其一即可完成面的绘制）

virtual Adesk::Boolean mesh(const Adesk::UInt32 rows,
const Adesk::UInt32 columns,
const AcGePoint3d* pVertexList,
const AcGiEdgeData* pEdgeData = NULL,
const AcGiFaceData* pFaceData = NULL,
const AcGiVertexData* pVertexData = NULL,
const bool bAutoGenerateNormals = true
) const = 0;

virtual Adesk::Boolean shell(const Adesk::UInt32 nbVertex,
const AcGePoint3d* pVertexList,
const Adesk::UInt32 faceListSize,
const Adesk::Int32* pFaceList,
const AcGiEdgeData* pEdgeData = NULL,
const AcGiFaceData* pFaceData = NULL,
const AcGiVertexData* pVertexData = NULL,
const struct resbuf* pResBuf = NULL,
const bool bAutoGenerateNormals = true
) const = 0;

3）需要获取当前用户采取什么模式预览：

virtual AcGiRegenType regenType() const = 0;

还回值为枚举型

三。实现流程

1）首先创建一个继承自AcDbEntity的自定义实体类，将几个必须由自定义实体类

实现的虚函数声明!

2）绘制你的自定义实体：

void AcDbMyEntity::MyEntityShell(AcGiWorldDraw *mode, const AcGePoint3d &ptBase, INT32 xLen, INT32 yLen, INT32 zLen)
{const INT32 POINT_COUNT = 8;AcGePoint3d ptList[POINT_COUNT] = {};INT32 index = 0;ptList[index++].set(ptBase[X],			ptBase[Y],			ptBase[Z]);ptList[index++].set(ptBase[X] + xLen,	ptBase[Y],			ptBase[Z]);ptList[index++].set(ptBase[X] + xLen,	ptBase[Y] + yLen,	ptBase[Z]);ptList[index++].set(ptBase[X],			ptBase[Y] + yLen,	ptBase[Z]);ptList[index++].set(ptBase[X],			ptBase[Y],			ptBase[Z] + zLen);ptList[index++].set(ptBase[X] + xLen,	ptBase[Y],			ptBase[Z] + zLen);ptList[index++].set(ptBase[X] + xLen,	ptBase[Y] + yLen,	ptBase[Z] + zLen);ptList[index++].set(ptBase[X],			ptBase[Y] + yLen,	ptBase[Z] + zLen);Adesk::Int32 faceList[] = {4, 0, 1, 2, 3,4, 4, 5, 6, 7,4, 0, 1, 5, 4,4, 1, 2, 6, 5,4, 2, 3, 7, 6,4, 3, 0, 4, 7,};INT32 faceLen = sizeof(faceList) / sizeof(faceList[0]);AcGiFaceData faceData;INT32 baseColor = 10;INT32 incColor = 30;short colors[] = {(baseColor += incColor),(baseColor += incColor),(baseColor += incColor),(baseColor += incColor),(baseColor += incColor),(baseColor += incColor)};faceData.setColors(colors);mode->geometry().shell(POINT_COUNT, ptList, faceLen, faceList, NULL, &faceData);
}

这里我采用的是shell()，当然mesh()也是可以的，简单说一下这个函数，如facelist

第一组属性，{4,0,1,2,3,****}

第一个数字4表明此面是由4个点组成，后面0,1,2,3是ptList中点的索引，由此4点组

成一个面，后面几组数值以此类推！

3）支持二维三维显示：

Adesk::Boolean AcDbMyEntity::subWorldDraw (AcGiWorldDraw *mode) {assertReadEnabled () ;INT32 xBase = m_ptBase[X];INT32 yBase = m_ptBase[Y];INT32 zBase = m_ptBase[Z];INT32 xLen = m_len3D[X];INT32 yLen = m_len3D[Y];INT32 zLen = m_len3D[Z];switch (mode->regenType()){case kAcGiStandardDisplay:{const INT32 POINT_COUNT = 5;AcGePoint3d ptList[POINT_COUNT] = {};INT32 index = 0;ptList[index++].set(xBase,			yBase,			zBase);ptList[index++].set(xBase + xLen,	yBase,			zBase);ptList[index++].set(xBase + xLen,	yBase + yLen,	zBase);ptList[index++].set(xBase,			yBase + yLen,	zBase);ptList[index].set(xBase,			yBase,			zBase);mode->geometry().polyline(POINT_COUNT, ptList);m_enShowMode = en2D;}break;;case eAcGiRegenTypeInvalid:case kAcGiHideOrShadeCommand:case kAcGiRenderCommand:case kAcGiForExplode:case kAcGiSaveWorldDrawForProxy:{MyEntityShell(mode, m_ptBase, xLen, yLen, zLen);}default:break;;		}return (AcDbEntity::subWorldDraw (mode)) ;
}

四。效果截图：

1）三维实体，每一面都有特定颜色，可以简单的加宽